132 Heredity. 



other breeds, the chickens often have five toes on one 

 foot and four on the other. 



When the red flowered stock of Antirrhinum is ferti- 

 lized with the pollen of the purple Queen stock, about 

 half the seedlings resemble the mother plant, while the 

 other half bear rich purple blossoms like those of the 

 paternal plant. 



Darwin says that he fertilized the purple sweet-pea, 

 which has a dark reddish-purple standard-petal and vio- 

 let-colored wings and keel, with pollen of the painted- 

 lady sweet-pea, which has a pale cherry- colored standard 

 and almost white wings and keel, and from the same 

 pod twice raised plants resembling both sorts, the greater 

 number resembling the father. 



These cases are difficult to explain, but the phenomena 

 are so complicated that it is hardly safe to speculate 

 upon them until they are re-examined by an observer who 

 can devote himself to this subject especially. 



Some of them may be due to the causes above indi- 

 cated, and some, possibly, to fertilization by two fathers. 



Crossing as a Cause of Reversion. 



According to Darwin's view reversion must in all cases 

 be due to the manifestation of a tendency which has lain 

 dormant in the egg and has been transmitted for gener- 

 ations in a latent condition, for the chances against the 

 repetition, by an accidental variation, of a characteristic 

 of a remote ancestor, are inconceivably great. 



According to our theory this is not the case, for the 

 conditions which caused a cell in the ancestral form to 

 throw off gemmules and thus to produce a given pecu- 

 liarity may cause the corresponding cell of the parent to 

 throw off gemmules in the same way, and these, uniting 

 with the corresponding part of the egg, will produce 



